Corrosion prevention



March 12, 1957 A. c. LANTERI 2,785,089

CORROSION PREVENTION Filed Mar'ch 25. 1954 United States Patent j2,785,089 CORROSIGN PREVENTION Albert C. Lanteri, New York, N. Y.,assignor to The Texas Company, New York, N. Y., a corporation ofDelaware I Application March 23, 1954, Serial No. 418,237 7 Claims. (Cl.117-97) The present invention relates to protecting metal bodies againstcorrosion, especially the inner surfaces of tanks and vessels. Moreparticularly, it is 'concerned with applying and maintaining an adherentprotective coating to the interior surfaces of ballast tanks and thelike formed of ferrous materials and subjected to the corrosive eect ofair and water, particularly salt Water. Other tanks which may beprotected by the invention are Colfer dams, bilges, voids, rudders, 'drydocks, and iire tower water tanks. l

This application is a continuation-in-part of my application Serial No.275,853, led March l0, 1952, and now abandoned.

In accordance with the present invention, an eifective rust preventivecoating is applied to the interior walls of the vessel, tank orcontainer by introducing a iluent composition comprising a relativelyviscous petroleum r'esiduum from a naphthene base crude oil (formerlyknown as an asphaltic crude), a relatively fluid light petroleum oil,and a surface active agent effective to increase the adhesivitiyv of thecomposition to solid surfaces. The composition is oated upon the surfaceof a body of water as a uniform layer of substantial thickness and thewater level is thereafter progressively altered, leaving a uniformprotective coating strongly adhering to the walls of the vessel.

For example, the composition is placed in the bottom of a tank, andthereafter water is introduced below the composition to form a oatingsurface layer. The water level is continually raised by pumpingadditional water into the lower part of the tank. As the Water risesupwardly, the composition continues to float on the lupper surface as auniform, unbroken layer, which, at its margins, makes uniform contactwith the interior surfaces of the vessel, merging therewith and leavinga continuous, uniform and highly adherent film. Alternatively, the tankmay be lled with water, the surface layer of composition introduced, andthe water thereafter drained to effect surface coating. One embodimentof the invention is lshown by the drawing. Figure l illustrates a tankwith a layer of the corrosion inhibiting composition on the bottom ofthe tank. Figure 2 illustrates the same tank after water has beenintroduced to raise lthe level of the corrosion Vinhibiting compositionand r'to coat the sides of the tank.

It is believed surprising that even in the presence of moisture, thefluent coating l'material repels the surface moisture and bonds with theinterior surfaces of the vessel to form a substantial, highly adhesivelm which remains continuously in place in spite of repeated draining andrelling oi 'the tank and violent agitation of its contents. Sincecontact of water or atmosphere with vthe ferrous Vsurfaces isee'ctive'ly prevented by the resultant coating, the objectionablerusting or corrosion which otherwise takes place in' vessels of thischaracter' is effectively overcome.

The oating procedure Vof the present invention is of particularadvantage from the standpoint of obviating the high cost and diculty ofapplying a rust-preventive coating to the interior o'f a tank. Thecomplex interior structure of ship ballast tanks, Vfor example, madeforrner manual procedures economically undesirable `because staging hadto be built 'for inento Ywcrk on. Moreover, it has been proven to bediflicult by such manual means Patented Mar. 12, 1957 rice to obtain auniform coating over the entire interior surface', 'even where thesesurfaces are first prepared by chipping or sand blasting, because ofobstructions which hinder the workers. Accordingly, exposed spots,'cracks or thin areas tend to initiate points of rapid corrosion.

The present invention is based upon the discovery that the presentprotective coating material is inherently adapted to deposit a uniformadherent coating from a tiuent surface layer or lrn floating upon a bodyof Water. This is particularly surprising inasmuch as typical liquidcoating materials fail to exhibit the necessary water repellency andpreferential wetting properties necessary for application to metalsurfaces in this manner and even where there is some surface adherence,fail to provide the necessary depth and uniformity of coating. In directcontrast, the coating composition contemplated-in accordance with thepresent invention, as above indicated, adheres tenaciously even torelatively damp and unprepared surfaces in a layer which inherentlyassumes a substantial and uniform effective thickness, and is resistantto removal or penetration by washing, agitation or repeated wetting anddrying.

As above indicated, the invention is particularly advantageous in thecase of ship ballast tanks wherein substantial agitation of water in thetanks is frequently encountered. A small residual quantity of coatingmaterial may be permitted to remain on the surface of the water withinvthe tank or relatively small amounts-may be added periodically prior todischarging or taking on ballast, to render the protection a permanentone. This follows from the fact that the thickness of the coating isinherently determined by the properties of the coating material and,therefore, remains at the proper value in spite of repeated applicationin the manner contemplated.

The iluent coating material composition, in accordance 'withthe presentinvention, comprises a straight run 're- Siduum from a naphthene basetype of crude oil, as, for example, a high viscosity residual oil havingav Saybolt- Furol viscosity of 40-55 seconds at 210 F. Desirably thisresiduum constitutes 25-40% of the composition by volume. The residuum,per se, is ordinarily too viscous to ovv readily over the surface of abody of water and, therefore, it is cut or thinned to the desired uencywith a suitable petroleum stock which is miscible with the residuum toform a homogeneous solution.

For the present purposes, a composition is preferred having aSaybolt-Furol viscosity in thek range of about 25-50 seconds at 122" F.ln this range of fluency the liquid will spread uniformly across thesurface of l:the water making good Contact withk confining surfaces atits margins. A narrower preferred range of'viscosity for thecompositionis about Sil-4G seconds on the lsame basis of determination.

In preparing such a composition the residuum may be cut back to thedesired viscosity with a light lubricating distillate such as one havinga Sayholt-Universal viscosity Yof 10Q-175 seconds at 100 F., for examplel0!) seconds. in general the heavy residuum may he cut back with anylighter, liquid petroleum oil capable of lowering 'the viscosity of theresulting mixture to the desired range indicated above. Adv'antageouslymiddle distillates are selected having a ilash point above about 350 F.to avoid lire hazard. The light petroleum oil desirably constitutes5570% of the composition by volume.

The adhesivity increasing agent preferred in accordance with the presentinvention comprises tall oil as, for example crude tall oil, obtainableunder the trade name Liqro. The tail oil is in effect a surface activeagent Vwhich dissolvesrin the residuurn and oil and substantial- -lyincreases the adhesivity of the lresidunrn for vfrerif'riyl's, surfaces.Actually, the increase in adhes'vity ffvthe residuum is such as toconfer a wetting power higher than volumes of a non-refined distillatehaving a Saybolt- TABLE I that of water. As a result, the highlyadhesive coating material actually displaces surface moisture andsubstitutes therefor on the tank surfaces, forming a preferential andessentially permanent bond.

Moreover, such coatings actually penetrate or strike through rust, slimeor similar surface debris even in the presence of moisture. rl`hisaction is apparently enhanced by the presence of the lighter cutbackstock, but,

V:2,785,089 l' f in any event, the result is important from thestandpoint of obviating the costly surface preparation usually required.

ln its broadest aspect the invention contemplates substituting for thepreferred tall oil additive other materialsA coming within the class ofsurface active agents which `are effective to increase the adhesivity ofpetroleum Vresidua to solid surfaces and correspondingly promote classof agents has previously been recognized in the 'preparation ofmineral-bituminous Vaggregates for the preparation of bituminouspavements. It includes, for example, condensation products of a diaminewith alkyl or alkenyl substituted succinic or succinamic acids,anhydrides or acid esters thereof as disclosed in U. S. Patent No.2,482,586.V ln this class are also found the water-insoluble polyaminesobtained by hydrogenating the condensation product of an'alpha-betaunsaturated aldehyde and ammonia or an amine as disclosed in U. S.Patent No. 2,520,720. Also, mention is made of the use of combinationsof sulfur with an oleophilic aliphatic monoamine as disclosed in U. S.Patent No. 2,478,162.

It has also been discovered that a number of additional agents arespecifically effective as surface active agents to increase theadhesivity of the residuum and confer water repellency. Among these arepetroleum calcium sulfonate which is the calcium salt of sulfonatedliquid petroleum fractions. Also may be mentionedthe relatively longchain aliphatic nitriles as for example octadecane nitrile knowncommercially as Armeen T. In general these surface active agents areeffective in Vproportions of from about l-% by volume of thecomposition, and preferably about 3-5%. Higher percentages are notdisadvantageous but are unnecessary to confer adequate adhesivity andtherefore are uneconomic.

Following is one specific example of the present inven- -tion as appliedto a starboard ballast tank of an ore vessel having a width of about 14feet, a length of about 50 feet, about 50 feet deep and having acapacity of about 1,050 tons ballast water. The interior of the tank wasin typical condition of a ship ballast tank after an extensive vperiodof service, with extensively rusted, silted and slime coated surfaces.

For the treatment of this tank a coating compositionA lwas made up asfollows: 33.3 volumes of a 42-45 second Saybolt-Furol viscosity at 210F. straight run residuum produced from a naphthene base crude was cutwith 63.8

Universal viscosity of l-l45 seconds at 100 F. The mixture was completedby incorporating 2.9 volumes of crude tall oil. The resulting mixturehad a Saybolt- Furol viscosity of between and 40 seconds at l22 F.

and comprised a sticky, greenish-brown, highly adhesive Y but readilyfluent liquid material. its specic gravity wasrabout 0.9421 at F.compared with water at the same temperature. j A

About 300 gallons of the coating oil was pumped into the bottom of thetank and permitted to spread about. vl-inter was then introduced intothe bottom of the tank below the layer of coating material to cover thebottom and the coating material was permitted to form a uniform layerover the upper liquid surface, merging at its margins with theupstandiug walls of the tank.

T he rate of water introduction proceeded slowly at first to avoiddisruption of the floating layer and thereafter the rate Vof inow wasset at a convenient rate to fill the Y tank.

The result of this treatment was an unbroken, apparently uniform coatingover the interior walls of the ballast tank contacted by the oatinglayer, and by completely iilling the tank or by suitably agitatingvthecontained water, over the entire interior surface.

vAfter approximately tive months of continuous service the coatingremained uniformly adherent to the interior surfaces of the tank,indicating a phenomenal adhesive amnity or bonding effect for the metalsurfaces. It has been observed that the tall oil has a phenomenalaffinity for ferrous metals, such as iron and steel, and that it tendsto migrate thru the oily carrier and attach or plate itself against theferrous surfaces.

ln order to evaluate further Vthe rust Vand corrosion protectionafforded by the abovercomposition when applied to wet or dry metalsurfaces the following test was made. Six identical steel panels weresandblasted clean and weighed. Two ofthe panels were given two dipsthrough a one quarter inch layer of composition floating on the surfaceof a container of synthetic sea water. Two more of the panels were firstwet thorough- Y ly with synthetic sea water and then the composition wasY applied in the same way as on the first two panels.

The remaining two panels were used as blanks; one was left dry and theother wasV wet with synthetic sea water. All sixpanels were hung outsidein the open air for one month.

After the one months exposure Vall of the panels were washed inprecipitation naphtha and acetone to remove the composition andV water.The panels were then dipped ina saturated solution of oXalic acid toremove any loose rust, rinsed in plain water, dried in an oven at 250 F.and weighed. No effort was made to remove the rust mechanically. Table Ishows the change in appearance of the panels as the test progressed andalso the weight changes after one months exposure. It is evident thatgood protection against rust and corrosion was obtained regardless ofkwhether the metal surface was wet or dry at time of application. Y

Outdoor exposure test Y Dry Panels Plus Composition Wet Panels PlusComposition Test Duration, Days Dry Panel Unprotected Wet PanelUnprotected Y Y Number 1 Number 2 y Nurnb er 1 Number 2 1 Numerous spotsof 100% light rust Clean Clean. speaks oi rust.

100% moderate rust Spots of rust Same as No. 1. do do Do. 100% moderateto heavy Numerous spots Do.

rust. and: streaks of l rus 21 100% moderate to heavy 100% heavy rust75% light rust--. Do.

. ru t 30 100% heavy rust do Spots oi-rust .f Same as No. 1;.. 90% lightrust-.. 95% light rust. Weight o hange mg. gain 275 mg. gain.-. 5 mg.1oss..-- 1 mg. gain 8 mg. gain 15 mgngain.

Continuous immersion of steel in water is a fainy severe rusting andcorroding condition, but it is not as severe as Ia cycle of alternatingperiods of immersion in water followed by exposure to air. Consequentlya cycle `of this type was used to evaluate the protectivity of thecomposition. Y

A set of eight steel panels was irst sandblasted and weighed. Four ofthe panels were dipped in the composition, but the other four panelsreceived no protection. The eight panels were then immersed in syntheticsea water for one day followed by hanging in air for one day. This dailycycle was repeated for eight Weeks. One protected and one unprotectedpanel were removed after the first, second, fourth and eighth week. Whenremoved the panels were each washed in solvent to remove anycomposition, Wire brushed to remove rust, dried, and then weighed todetermine Weight loss due to rust and It is evident that the compositionajorded a considerable degree of protection in this severe test. Aftereight weeks the daily dunking in sea water had washed 0E a considerableamount of the composition, but the protected panel had still suieredonly about half as much weight loss as the Iunprotected panel.

In general it appears that etective surface coating may be realized withany floating layer of the coating material of sucient thickness whichwill inherently spread across the entire upper surface of the floodingwater to contact the conning surfaces at its margins. Preferably,however, a thickness of at least IAG to 1/2 inch is advisable.

The rate of water level alteration within any practically attainablerange docs not appear to exert any material etect on the character ofthe resulting wall coating so long as the oating layer of coatingmaterials, as above indicated, is su'icient to form a substantialuniform and unbroken stratum which makes contact with the interior tanksurfaces at its margins. Sometimes several passes of the coatingcomposition in a tank may be necessary to form an adequate iilm, thisbeing accomplished by repeatedly raising and lowering the water level.

As also intimated, the present process results in the coating ofinterior tank structures of the tank such as ladders, gussets, frames,bafdes and the like. It is also applicable to tanks in ygeneral whichare subjected to oontact with air and/ or aqueous liquids.

The composition of the invention is also valuable even where thefloating procedure cannot be employed, as for unenclosed metalstructures. Spraying or brushing can be used in such cases.

Obviously, many modifications and variations of the invention `ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore only such limitations should be imposedas are indicated in the appended claims.

I claim:

l. A method of inhibiting the corrosion 4olf a ferrous metal body whichcomprises applying to and maintaining on the surface of such a body ailuent coating composition comprising an intimate mixture of tall oil,petroleum residuum from straight run distilling a naphthene base crudeoil, said residuum having a Saybolt-Furol viscosity of 40-55 seconds at210 F., and suiicient petroleum oil of lower viscosity than saidresiduum to cut back said residuum and form a -composition having aSaybolt-Furol viscosity in the range of about 25 to 50 seconds at 122F., said tall oil being present in an amount between about 1 and 5% ofsaid composition.

2. A method for protecting the inner walls of a metal tank fromcorrosion which comprises introducing into said tank a fluent coatingcomposition comprising an intimate mixture of tall oil, petroleumresiduum from straight run distlling a naphthene base crude oil, saidresiduum having a Saybolt-Furol viscosity of 40-55 seconds at 210 F.,and sucient petroleum oil of lower viscosity than said residuum to cutback said residuum and form a composition having a Saybolt-Furolviscosity in the range of about 25 to 50 seconds at 122 F., said talloil being present in an amount between about 1 and 5% of saidcomposition; oating said coating composition upon the surface of a bodyof water in said tank as a uniform layer contacting the conning walls ofsaid tank at its margins; and coating said confining walls with saidcoating composition by eecting relative movement between the surface ofsaid body of water and said walls.

3. A method in accordance with claim 2 wherein said petroleum residuumconstitutes about 33.3%, Said petroleum oil constitutes about 63.8% andsaid tall oil constitutes about 2.9% of said composition.

4. A method in accordance with claim 2 wherein said petroleum oil has aviscosity of about -175 seconds Saybolt-Universal at 100 F.

5. A uent coating composition having the property of floating on waterand suitable for application by Water otation to the inner Walls of ametal tank to protect said tank from corrosion, said compositionconsisting essentially of 1 to 5% of tall oil, residual oil fromstraight run distilling a naphthene base crude oil, said residual oilhaving a Saybolt-Furol viscosity of 40-55 seconds at 210 F., andsufficient petroleum oil of lower viscosity than said residual oil tocut back said residual oil and form a composition having a Saybolt-Furolviscosity in the range of about 25-50 seconds at 122 F.

6. A uent coating composition in accordance with claim 5 wherein saidresidual oil constitutes about 33.3%, said petroleum oil constitutesabout 63.8%, and said tall oil constitutes about 2.9% of saidcomposition.

7. A uent coating composition in accordance with claim 5 wherein saidpetroleum oil has a viscosity of about 100-175 seconds Saybolt-Universalat 100 F.

References Cited in the tile of this patent UNITED STATES PATENTS

1. A METHOD OF INHIBITING THE CORROSION OF A FERROUS METAL BODY WHICHCOMPRISES APPLYING TO AND MAINTAINING ON THE SURFACE OF SUCH BODY AFLUENT COATING COMPOSITION COMPRISING AN INTIMATE MIXTURE OF TALL OIL,PETROLEUM RESIDUMM FROM STRAIGHT RUN DISTILLING A NAPHTHENE BASE CRUDEOIL, SAID RESIDUUM HAVING A SAYBOLT-FUROL VISCOSITY OF 40-55 SECONDS AT210%F., AND SUFFICIENT PETROLEUM OIL OF LOWER VISCOSITY THAN SAIDRESIDUUM TO CUT BACK SAID RESIDUUM AND FORM A COMPOSITION HAVING ASAYBOLT-FUROL VISCOSITY IN THE RANGE OF ABOUT 25 TO 50 SECONDS AT122*F., SAID TALL OIL BEING PRESENT IN AN AMOUNT BETWEEN ABOUT 1 AND 5%OF SAID COMPOSITION.